Slashdot Mirror
Black Holes...Pink?
st. augustine writes "Australian astronomers have discovered that some black holes are actually pink. Here's a Wired article, and here's the Australians themselves. I was more excited before I found out they were already expecting the black holes to be blue. "
Pink holes
You answered your own question. Any redshifted light would be counteracted by the blueshifted light. This is one reason why we see spread in the emission lines from Quasars. (part of the emission line is blue shifted and the other part is redshifted, so the line spreads out) The pink light is from something else. . . probably material in the acretion disk of the black hole.
I couldn't tell if you were experimenting with poor-man's cryogenics or looking for the orange sherbet.
When seeking information on the Internet about important new developments in astrophysics, using the search term "pink holes" will probably not give you completely satisfactory results with most search engines, even though the hit count may be large.
These objects are distant quasars. The quasar population was largest when the universe was around a third of its present size (a redshift of 2) and about a fifth (specifically, one 3*sqrt(3)th) of its current age. At this distance, which is around ten billion light years, the resolution of ground-based telescopes is around five thousand light years (this is a limit set by the Earth's atmosphere). So we know that the whole galactic nucleus of the host galaxy, as viewed by us, is "pink". A quasar should dominate the light output from this region- and the light is emitted from a region a few light-days across. This is known because quasars vary in brightness on timescales of weeks.
When astronomers refer to colors, typically "red" or in this case "pink" refers to emission of larger amounts of light at long wavelengths at short ones. Given the telescopes used, I would guess that they were observing in the "optical" band, which is from around 350 nm (near UV) to around 800 nm (infrared). These would be emitted by the quasar as UV and would lengthen into this band in the observer frame. At redshift 2, these would be emitted at 117 to 267 nm. So, a better headline would be "black holes found to emit more near-UV than far-UV". Of course, this wouldn't be very striking.
The accepted mechanism for quasar action is that matter falls toward a black hole, collides with other matter, and emits radiation. In fact, there is an equilibrium where the matter falling in produces enough radiation that radiation pressure keeps more matter from falling in. This process should be very hot and so should produce light that is "blue" even in the far UV region.
There are, however, some additional details of the procedure. Some quasars have what are called "jets" of ejected material. We know these are extremely fast because the apparent velocity across the line of sight exceeds the speed of light in many cases. This is allowed by relativity if the jet moves at a speed near the speed of light pointing directly at us. The jet phenomenon is believed to be connected with a preferred axis of rotation for the material falling into the black hole, and with "synchrotron radiation" emitted by charged particles accelerated by the black hole's gravity. The report seems to suggest that the "pink" light is connected with the jet phenomenon, perhaps in cases where the jet is pointed directly at us.